My new paper is out today and it describes a wonderful new specimen of four baby Protoceratops together in a single block. Unlike many other groups of exceptionally preserved specimens from the Mongolian Gobi, the animals are effectively stacked on top of one another and all facing in different directions and importantly, their inferred age is different to other Proto specimens.
This specimen was actually collected in the early 1990s, something I hadn’t realised when I saw it in 2011 in the Hayashibara museum in Japan. This was my second trip to the museum after having been in 2009 (that led to the Tarbosaurus bite marks paper) and this was the specimen that really grabbed me and I am obviously most grateful to co-author Mahito Watabe for allowing me to lead the paper on this.
The preservation is superb, and although there’s been some erosion and damage (especially to the uppermost animal) at least one of them is brilliantly exposed and almost immaculate in condition. At this point I must praise the preparator for his incredible work here, this is a huge block (close to a metre cubed), the matrix is exceptionally soft and brittle and the organisation of the specimens must have made the whole process extremely difficult and the result is both beautiful and impressive.
There are two major aspects to the paper (which is in PLOS ONE so for all the details and tons of pics so you can read it all there) and I’ll deal with them in separate posts. The first one is the block itself and the implications for Protoceratops generally. There are a number of groups of this dinosaur known already – several sets of adults, a pair of subadults (also briefly covered in the paper – and shown below) and a set of very young animals that were described a few years ago as something close to hatchlings in a nest. In the paper we actually suggest that these were not in a nest, but free living, but the wider point is that we have similar sized animals (that are probably of a similar or the same cohort) together at multiple different life stages, and we don’t seem to see mixed cohorts as with many other dinosaurs.
The block here slots into this pattern beautifully, the animals are about twice the length of the smallest ones, and about half the size of the subadults. That means we can put together a sequence of specimens at four pretty distinct life stages where we have groups of animals together at different times of their lives. That is something we have not been able to do for any extinct dinosaurs before – we do often have groups together and often of adults or juveniles or the two mixed together, but we are not aware of a so many obviously different cohorts of a single species showing this. Wonderfully, these are not all just Protoceratops, but all P. andrewsi and even better all of these are from a relatively narrow time and space window.
As non-avian dinosaurs go, that’s about as close to a single population as you are really going to be able to find, so collectively we are inferring that this was a pretty normal behaviour for this population. That sounds like a pretty conservative approach (can we not apply it to the genus or species as a whole?), but I think it’s something we really need to do a lot more of in palaeontology. The sheer variety and plasticity of many behaviours, especially when it comes to forming groups, means that is probably dangerous to extrapolate without some good supporting evidence and that sets things up quite nicely for the second post which will follow tomorrow.